Hi, first of all thanks for all the work, it's pretty impressive, and very helpful.
It seems that the files you replaced before on the suggestion of Rufus (menu.c32 and vesamenu.c32) were actually changed from their Syslinux 6.03 version to their Syslinux 4.07 version.
Following that constatation, I tried to replace the other .c32 files by their Syslinux 4.07 and it corrected some things which didn't work before (rebooting or continuing booting the PC).
But I still had some errors during the boot. It did confirm though that the syslinux installed was a 4.07, while the modules were in 6.03.
Then even better, I asked Rufus to create a blank Syslinux 6.03 on my flashdrive (you need to activate advanced features for it to be available in the list), then :
- extracted the files from the .iso (using 7zip)
- added the syslinux.cfg I had kept from a precedent try (7zip doesn't find it in the archive, for some reason I don't understand since I don't know much about ISO files)
- replaced menu.c32 and vesamenu.c32 with their 6.03 version
(I actually added these 3 files before the iso extraction, but I don't think it matters)
And it seems to work perfectly, without error messages, except for the poweroff (it's possible that it's not supposed to work on my computer anyway).
I didn't check all the functionalities (far from it, given their number), and I don't understand every issue involved, but I thought I would share about my experiments so that others can test it too and in case it should help to find a better solution.
For those who want to try, I'm attaching the files I added/replaced (menu.c32, vesamenu.c32, syslinux.cfg)